The purpose of the study was to determine if drug abuse treatment is cost effective in the treatment of pregnant drug abusing women. Neonatal intensive care unit (NICU) and drug abuse treatment costs were compared in two groups of pregnant drug abusing women the first 100 admissions delivering in a comprehensive treatment program and 46 controls who did not enter drug abuse treatment but were ascertained through obstetrical services at a sister hospital serving the same urban catchment area. Clinical measures included urine toxicology at delivery, infant birthweight, Apgar score, and need for and duration of NICU services. Cost measures included drug treatment and NICU costs. Comprehensive care patients showed improved clinical outcome at delivery, with less drug use and higher infant estimated gestational age (EGA), birthweight, and Apgar scores. Infants of such patients were also less likely to require NICU services and, for those that did, had a shorter stay. When total cost was examined, net savings for comprehensive care subjects was $4,644 per treatment episode per mother/infant pair. The study demonstrates the cost effectiveness of comprehensive treatment for pregnant drug abusing women, with a savings in NICU costs exceeding the costs of drug abuse treatment.